<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>demo1</title>
    <script src="js/js1.js"></script>
</head>
<style>
    .main{
        height: 100px;
        width: 100px;
        border: 1px solid;
        /*margin-right: auto;*/
        /*flex: 1;*/
    }
    #top{
        display: flex;
    }


</style>

<body>
<div id="top">
<div id="left" class="main">1</div>
<div id="center" class="main">2</div>
<div id="right" class="main">3</div>

</div>

</body>
</html>